The nature and extent of harm from adverse events (AEs) taking place in ambulatory care has received considerably less regulatory and improvement attention than AEs observed as part of inpatient care. Accordingly, the Baylor Health Care System has modified in content and process the IHI Outpatient Trigger Tool (I-OTT) to evaluate care received by patients seen by primary care physicians employed by HealthTexas Provider Network (HTPN). A revised instrument - the Baylor/IHI Outpatient Trigger Tool (Bl-OTT) was used in 2006 to evaluate the care of 5,246 patients who received care from 179 primary care physicians during 2005. This review has allowed initial estimates of the extent, pattern and nature of AEs related to care during 2005. Major findings include the existence of 25.6 adverse events per 100 patient years of care for audited adult patients that met the criterion of requiring some additional level of care/monitoring. Approximately 54% of AEs had some level of perceived preventability, 80% were associated with the care that was provided (vs. 20% related to indicated care that was not provided) and 63% were associated with the PCP's care (46% were associated with patient responsibility and 25% with care provided outside the PCP's practice). These data indicate that there is considerable patient risk in ambulatory primary care and strongly encourages the proposed specific aims related to the broad goals of: a) refining and characterizing the BI-OTT instrument/audit process for broader use to more accurately estimate the burden of harm to primary care patients; and b) using this relatively nonbiased approach to select events for in depth study to evaluate the nature of the threats/risks that contribute to the observed [unreadable] AEs. The results of the proposed research will: 1) generate a mature audit instrument/process (including electronic data collection tools and training manuals) that can be used to quantify AEs in ambulatory environments broadly; 2) provide a large scale estimate of the extent, nature and source of AEs with sufficient generalizability to begin to estimate this burden upon adult patients in the US; 3) establish the underlying high risk care processes that contribute to the development of AEs that do NOT depend upon more biased ways to identify them; 4) estimate the burden of AEs that are amenable to prevention or amelioration as a result of risk mitigation. The more mature BI-OTT2 audit instrument / process will provide the opportunity to: a) measure the effectiveness of interventions designed to improve patient safety in ambulatory primary care; b) permit longitudinal evaluation of the experience of patients with an identified AE (related to their clinical and economic outcomes); c) permit evaluation of similar patient outcomes that derive from care in practices that demonstrate higher vs. lower rates of AEs as identified through use of the Bl-OTT2. [unreadable] [unreadable] [unreadable]